1. 1.1 b – The structure and function of the muscular system
Learning objectives
To be able to label all major muscle groups in the body.
To understand the terms; Agonist, Antagonist and Fixator.
To be able to explain the meaning of an antagonist pair and provide examples.

2. Muscles of the body Watch me
Muscles are used in everyday life all the time. Sportspeople are reliant on the power of muscles to perform at the highest level.
Photo by: © paddynapper on Flickr. This image is reproduced under the terms of the Creative Commons License 2.0.
Photo by: © deshow.net
Watch me
What do you know about muscles already?

3. Muscles Types There are 3 main muscle types. Voluntary Involunatary
Cardiac

4. Skeletal or Voluntary Muscle
Task: Complete the table.
Type of Muscle
Involuntary Muscle
Cardiac Muscle
Skeletal or Voluntary Muscle
Main Features
Examples

5. How many voluntary muscles do you already know?
Competitive Challenge : in pairs write down the names of muscles you already know – which couple can identify the most? In the event of a draw you will be asked to locate each of the muscles you have listed.

6. Voluntary Muscles Trapezius Pectorals Triceps Deltoid Latissimus Dorsi
Bicep
Gluteals
Abdominals
Hamstring
Quadriceps
Photo: © Stock.xchng.
Gastrocnemius

7. Voluntary Muscles
Muscles shorten when they contract and lengthen when they relax.
Photos: © Stock.xchng.
Think. Pair. Share - What happens when muscles contract?

8. Muscle
Movement
Deltoid
Execution of a block in volleyball
Trapezius
Execution of a rugby forward in a scrum
binding into the opponents
Latissimus Dorsi
Preparation phase of a forehand
groundstroke in tennis
Pectorals
Execution of a rugby player making a
tackle holding onto his opponent
Biceps
Execution of the upward phase of bicep curl
Triceps
Execution of a downward phase of bicep curl
Abdominals
Execution of a sit up
Quadriceps
Execution of the take off in the long
jump
Hamstrings
Preparation phase of kicking the ball in
football
Gluteals
Execution of a sprinter performing the 100
metres
Gastrocnemius
Execution of a swimmer pointing
their toes in the front crawl leg action

9. Antagonistic muscle action – Key terms
Definition
Insertion
This is the end of the muscle
attached to a bone that actively moves when
contraction occurs.
Origin
This is the end of the muscle attached
to the bone that is stable. This remains still
when contraction occurs.
Agonist
Working muscle that produces or
controls the desired movement (also known as
prime mover).
Antagonist
The movement caused by the
agonist is countered by the action of the
opposing muscle.
Fixator
The function of a fixator muscle is to stabilise the origin of the agonist muscle so that it can move efficiently

10. Antagonistic muscle action
There are three important features to a joint. The agonist, antagonist and fixator muscle.
At the elbow joint the agonist is the bicep muscle.
The tricep here is the antagonist
Photo: © Stock.xchng.
The function of a fixator muscle is to stabilise the origin of the agonist muscle so that it can move efficiently. i.e. the rotator cuff in the deltoid region for the shoulder.

11. Understanding muscle action
Muscles are attached to bones by tendons.
The tendon at the non-moving (or fixed) end is known as the origin.
The tendon at the moving end is known as the insertion.
Muscles pull by contracting – they cannot push to produce the opposite movement.
Muscles are arranged in antagonistic pairs.
As one muscle contracts (shortens) its partner relaxes (lengthens). They swap actions to reverse the movement.

12. Quadriceps / hamstring muscle action
The quadriceps and hamstrings in the legs are another antagonistic pair. Can you answer the following questions?
Which joint do they move?
quadriceps
What types of movement are produced?
hamstrings
Which is the flexor and which is the extensor?

13. Antagonistic muscle action
Photos: © adamkr on Flickr. This image is reproduced under the terms of the Creative Commons License
Hamstring and Quadricep acting at the knee joint. The movement at the driving knee is flexion. What is the agonist? What antagonist? Origin and insertion?

14. Hamstring and Quadricep acting at the knee joint
Hamstring and Quadricep acting at the knee joint. The movement at the leading knee is extension. What is the agonist? What antagonist? Origin and insertion?

15. Muscular system Apply it! What has stuck with you?
Name the agonist and antagonist muscles at the knee joint during flexion?
Explain what is meant by an antagonistic pair and an example in the body?
Highlight on your body as many major muscle names as possible.
Analyse the major muscles working at the
a) Knee joint
b) Shoulder joint
Muscular system

16. Practice it! Exam questions
1. The image shows someone performing a bicep curl.
Name the agonist and the antagonist muscles used when performing this move (1)
Agonist: …………………………………………………………………………..
Antagonist: ………………………………………………………………………

17. Practice it! Exam questions
2. Fig.1 shows a diagram of the knee. Label the muscle group A and the bone B.

18. Practice it! Marks Scheme: Agonist – Biceps Antagonist – Triceps
Muscle group A – Quadriceps Bone B – Femur